1. Field of the Invention
This application concerns an improved fuel injector of the electromagnetically actuated type for an internal combustion engine. The injector includes structure to precisely control the closing characteristic of its valve which opens and closes to regulate fuel flow to the engine. This produces an extremely accurate fuel delivery for each opening and closing cycle. In contrast, other fuel injectors exhibit relatively imprecise valve closing control which usually results in valve rebound or bounce away from the valve seat surface occurring after valve closure. This valve rebounding or bouncing produces secondary valve openings and therefore increased fuel delivery to the engine per opening and closing of the injector. The excess fuel flow decreases combustion efficiency. Also, it has been found that the fuel delivered during valve rebound is usually poorly atomized, further resulting in combustion inefficiencies.
Valve rebound results from the recovery from an elastic deformation of the valve and valve seat caused by the closing impact. The subject fuel injector inhibits significant valve rebound or bounce by generating an opposing force on the valve. The opposing force is produced by the rapid formation of a relatively low pressure of the fluid between the valve and its support structure as the valve tends to move away from the seating surface after valve closure.
2. Description of Related Art
An objective of the fuel injector is accurate fuel delivery to an associated engine or a specific combustion chamber. With an electromagnetically actuated and electronically controlled injector, a control unit or computer directs opening and closing of the valve. The subject injector is pulse width modulated which is particularly adapted for controlling fuel delivery to a single cylinder. This general type of injector is available on several vehicle engines made by Chrysler Corporation. The quantity of fuel delivered during each combustion event by the pulse width modulated injector is determined by the period of time that the computer maintains the injector valve in an opened operative position. This period of time is selected by the computer which receives various engine operating inputs such as engine speed, load, and vehicle speed. To deliver the predetermined correct quantity of fuel for each combustion event, it is expected that the valve will open and then close precisely. If the valve rebounds even once from its seating surface after closing, a considerably greater quantity of fuel may be delivered than planned. Excessive fuel delivery caused by valve rebound is amplified when the injector operates at relatively high fuel pressures.
In a pre-examination patent search, a substantial number of prior patents have been uncovered. None of these patents disclose fuel injectors or the like with means to inhibit valve rebound or bounce by producing a rebound inhibiting force due to a decreased hydraulic pressure between the surfaces of an injector valve and a support structure. The following U.S. Pat. Nos. were uncovered: 1,252,254; 1,498,034; 4,168,804; 4,186,708; 4,231,525; 4,245,789; 4,247,052; 4,275,844; 4,275,845; 4,306,680; 4,331,317; 4,342,427; 4,375,274; 4,392,612; 4,406,404; 4,434,765; 4,515,129; 4,520,962; 4,572,146; 4,621,772; 4,795,097; 4,971,254; and 5,012,981.